Composite ignitor and arc lamp holder assembly

ABSTRACT

An arc lamp holder includes an axially directed air duct containing a socket into which the base electrodes of a sealed beam arc lamp are inserted for making electrical connection to the arc lamp. An ignitor assembly which includes a toroidal transformer is coaxially mounted of and surrounding the air duct. The ignitor circuitry includes a primary winding connected in circuit with a charging capacitor and a spark gap element. The capacitor is formed by a plurality of parallel connected disc capacitors mounted in a circular array to form a relatively large storage capacitance which is discharged through the spark gap and primary winding of the transformer to produce a high step up voltage applied to the arc lamp for starting thereof. The step up transformer, storage capacitor and spark gap are embedded in a dielectric potting material forming an integral portion of the lamp holder assembly.

United States Patent Souza July 8, 1975 COMPOSITE IGNITOR AND ARC LAMP Inventor:

Assignee: Varian Associates, Palo Alto, Calif.

Filed: Mar. 30, 1973 Appl. No.2 346,536

References Cited UNITED STATES PATENTS 11/1919 Lowenstein 313/46 X 2,770,745 ll/l956 Manfredi 313/36 X 3,343,019 9/1967 Wolf et al. 313/36 X FOREIGN PATENTS OR APPLICATIONS 1,075,752 6/1953 Germany 313/22 X 245,672 1/1926 United Kingdom 315/276 Primary ExaminerR. V. Rolinec Assistant ExaminerLawrence J. Dahl Attorney, Agent, or Firm-Stanley Z. Cole; John J. Morrissey [5 7] ABSTRACT An arc lamp holder includes an axially directed air duct containing a socket into which the base electrodes of a sealed beam arc lamp are inserted for making electrical connection to the arc lamp. An ignitor assembly which includes a toroidal transformer is coaxially mounted of and surrounding the air duct. The ignitor circuitry includes a primary winding connected in circuit with a charging capacitor and a spark gap element. The capacitor is formed by a plurality of parallel connected disc capacitors mounted in a circular array to form a relatively large storage capacitance which is discharged through the spark gap and primary winding of the transformer to produce a high step up voltage applied to the arc lamp for starting thereof. The step up transformer, storage capacitor and spark gap are embedded in a dielectric potting material forming an integral portion of the lamp holder assembly.

17 Claims, 5 Drawing Figures PATEHTEHJUL 8 ms 3.8 94,266

SHEET 1 FIG I SHEET a a a mdE COMPOSITE IGNITOR AND ARC LAMP HOLDER I ASSEMBLY BACKGROUND OF THE INVENTION The present invention relates in general to are lamp assemblies and more particularly to an improved arc lamp assembly including a composite ignitor and arc lamp holder.

DESCRIPTION OF THE PRIOR ART Heretofore, search lights have employed arc lamp assemblies mounted at the focal point of a parabolic reflector for reflecting the light emitted by the arc lamp into a sharply focused beam of light. In the past, armored vehicle such as tanks have employed such a search light mounted atop the turret for night operations. The problem has been that this type of a search light offers a relatively large silhouette making it a rela tively large target for enemy gunners.

In addition, this prior search light assembly included a separate lamp ignitor box of generally rectangular configuration mounted externally of the reflector and being of relatively large size, as of 40 cubic inches. The purpose of the ignitor is to provide a short burst of intensehigh frequency energy to be applied across the electrodes of the arc lamp to initiate the are which is then sustained by a relatively low voltage high current power supply.

Therefore, there exists a need for an improved search light assembly in which the search light and the associated ignitor are integrated into a small profile package.

SUMMARY OF THE PRESENT INVENTION The principal object of the present invention is the provision of an improved search light assembly having a relatively small profile.

In one feature of the present invention, a sealed beam arc lamp is contained within an axially directed fluid coolant duct of an arc lamp holder and a lamp ignitor including a toroidal step-up voltage transformer is disposed surrounding the fluid coolant duct, whereby a small-profile composite lamp holder and ignitor assembly is obtained.

In another feature of the present invention, the arc lamp ignitor circuit includes a primary winding coupled to a toroidal transformer; such primary winding being connected in circuit with a charging capacitor and a spark gap, and wherein the charging capacitor is formed by a circular array of parallel-connected disc capacitors disposed surrounding a fluid coolant duct of a lamp housing.

In another feature of the present invention, a composite lamp holder and lamp ignitor assembly is formed by a toroidal transformer coaxially disposed with respect to a circular array of charging capacitors, both being embedded in a dielectric potting compound having a central bore therethrough defining the air duct to contain the arc lamp in heat exchanging relation with a fluid coolant passing through the duct for cooling the lamp in use.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal sectional view of a search light assembly incorporating features of the present invention,

FIG. 2 is a plan view of a portion of the structure of FIG. 1 taken along line 22 in the direction of the arrows,

FIG. 3 is a side elevational view of the structure of FIG. 2 taken along line 33 in the direction of the arrows and being partially broken away to show the transformer core winding thereon, and

FIG. 4 is a schematic circuit diagram for the search light of FIG. 1, and

FIG. 5 is a fragmentary sectional view taken along lines 5-5 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown a search light assembly 11 incorporating features of the present invention. Thesearch light assembly 11 includes a lamp holder assembly 12 having a centrally disposed axially directed cylindrical bore or duct 13 adapted to receive a sealed beam arc lamp 14 having contactor electrodes on one end thereof mating with suitable contactor electrodes contained within an electrical socket 15 axially disposed within the duct 13. The are lamp 14 includes a forward threaded cylindrical lip portion 16 threadably mated with a reentrant portion 17 of an outwardly flanged adapter member 18. The flanged adapter 18 is secured to the forward end of the lamp holder 12 via cap screws 19 spaced at intervals around the periphery of the flanged adapter 18, as of at intervals.

In assembly, the arc lamp 14 is threaded onto the reentrant portion ofthe adapter member 18, and then the adapter is secured to the lamp holder 12 via the cap screws 19. This serves to pull the electrical contactors at the base of theme lamp 14 into electrical engagement with the electrical contactors of the socket 15, thereby assuring electrical connection to the arc lamp 14.

A perforated 'e'jlectrically insulative disc 21 is disposed at the forward end of the adapter 18 for holding the arc lamp 14 in electrical isolation from the lamp holder assembly 12. The perforated disc 21 includes a plurality of longitudinal bores or perforations 22 to facilitate the flow of coolant fluid such as air through the duct 13 and-apertures 22 to the surrounds of the housing for carrying away heat generated by the arc lamp l4.

More particularly, the arc lamp includes a first circular array of cooling fins 23 surrounding the arc lamp and coupled in heat exchanging relation to the lamp for conducting heat from the lamp into the coolant stream. In addition, a second circular array of cooling fins 24 similarly surrounds the arc lamp 14 to conduct heat from the narrow neck portion of the arc lamp 14 to the fluid coolant flowing through the duct 13. Air is typically used as the coolant fluid and is forced through the duct by means of a motorized fan 25 disposed in the duct 13 upstream of the socket 15.

A lamp ignitor assembly 26 is incorporated as an integral portion of the lamp holder 12. More particularly, the electrical circuit for the search light 11 is as shown in FIG. 4. The circuit includes an arc lamp 14 having an anode 28 spaced from a cathode 29 to define an arc gap 31 therebetween. The envelope of the arc lamp 14 is filled with a suitable gas of xenon to a pressure of, for example, 10 atmospheres.

In operation, the lamp 14 is ignitedbyapplying a short burst of high voltage radio frequency energy across the gap 31. In a typical example, the highintensity burst of radio-frequencyenergy has apeak-topeak voltage as of 30 kilovolts to initiate the arc. Once the arc is established, it is sustained by means of a relatively low direct-current voltage as of volts applied from a power supply across the anode to cathode electrodes via the secondary winding of a torroidal pulse transformer 32. A radio-frequency bypass capacitor 33 is connected across the positive and negative terminals of the low voltage power supply 30 for shunting the ignitor burst of radio-frequency energy around the power supply and across the gap 31.

The voltage step up transformer 32 has a primary winding 34 connectable across a relatively high voltage power supply 35 via a switch 36 and series resistor-37. A charging capacitor 38, as of 0.5 to 1.0 microfarads, is connected in series with the power supply 35 and the primary winding 34. A spark gap 39 is connected in shunt with the power supply 35 between the power supply and the charging capacitor 38. In a typical example, the primary winding 34 of the voltage step up transformer 32 has one turn, whereas the secondary winding 41 has between 60 and 65 turns for stepping up the voltage in the secondary over the primary voltage by a factor of approximately 30.

In operation, switch 36 is closed to charge the charging capacitor 38 to a potential which approaches the potential of the source 35, as of 2 kilovolts. When the voltage on the capacitor 38 exceeds the breakdown voltage of the spark gap 39, as of 1 kilovolt, the spark gap 39 breaks down and the capacitor 38 discharges through the spark gap 39 and primary winding 34 of the transformer 32 to produce the burst of high voltage radio-frequency energy in the secondary and across the gap 31 of the arc lamp 14 for igniting the arc therein. Due to the inductance of the primary winding 34 and the capacitance of the charging capacitor 38, the primary circuit rings with an exponentially decaying envelope. Once the arc is established in the arc lamp 14, the low voltage supply 30 maintains the arc and the lamp remains lighted. The switch 36 is then opened to deactivate the ignitor circuitry.

Referring again to FIG. 1 and to FIGS. 2 and 3, the ignitor assembly includes a toroidal ferrite core 44 of the step up voltage transformer 32 which coaxially surrounds the duct 13 and lamp 14. The one-turn primary winding 34 is wound around the core 44, and the secondary winding 41 is wound in the form of a helix around the core 44. The charging capacitor 38 is formed by a circular array of disc capacitors 45 mounted on an annular circuit board 46. The circuit board 46 and circular array of capacitors 45 coaxially surround the duct 13 and arc lamp 14. The spark gap 39 is mounted to the circuit board 46. The. capacitors 45, circuit board 46 and transformer 32 are embedded in a dielectric potting compound 47 as of epoxy resin to form a composite ignitor and lamp holder assembly The lamp socket 15 includes three radially directed hollow, insulative tubes 48 :through which wires make electrical connections to the socket 15 from the surrounding circuitry. The high voltage lead from the positive side of the transformer is brought through one of the hollow tubes 48 to the center terminal of the socket 15, whereas the cathode lead is brought throughan- 4 other one of the hollow tubes48 to the outer conductor of the socket l5. POWQ'flS supplied from power supplies 35 and low voltage power supply 30 through a connector assembly 49'at the base of the housing 12. Power is brought into-the fan motor 51 via connector 52.

In operation, the output light beam of the arc lamp 14 passes through .atransparent window 53, as of sapphire, at the forward end of the lamp 14. The output of the lamp, as of 15,000 to 16,000 lumens is focused to an external focal point 54 approximately 2.154 inches in front of the window 53. An optical system, not shown, collimates the output beam into a sharply defined search light beam.

The advantage to the search light assembly 11 of the present invention is that the profile of the search light has been greatly reduced such that the composite housing, ignitor and lamp structure, including the reflector, is contained within a lamp housing 12 having a length of approximately 9 inches, and an outside diameter of approximately 6 inches.

What is claimed is: 1

1. An arc lamp housingwhich comprises generally cylindrical wall means comprising an inner wall surface and an outer wall surface, said inner wall surface forming a duct, electrical socket -means being disposed within said duct for receiving a mating portion of an arc lamp, optical window means located within the duct of said housing, said optical window means being positioned so as to transmit light originating within said housing to the outside of said housing, are lamp igniting means being disposed between saidinner and outer wall surfaces, electrically conductive means extending from said igniting means into said duct for electrically connecting said igniting means to said socket, and means for causing a fluid to pass through said duct to cool said arc lamp during operation of said are lamp.

2. The are lamp housing of claim 1 wherein said means for causing a fluid to pass through said duct is disposed within said duct.

'-'3.=The arc lamp housing of claim 1 wherein said means. for causing a fluid to pass through said duct is a motorized fan for causing air to pass through said duct.

4. The are lamp housing of claim 3 wherein said fan is disposed within said duct upstream of said socket means with respect to the direction of air flow.

5. The are lamp housing of claim 1 wherein said are lamp igniting means comprises a transformer core, primary and secondary transformer windings in magnetically coupling relationship with said core, said primary winding being electrically connectable inseries to a first power supply located outside said housing, electrical resistance means and charging capacitance means being connected in series with said primary winding and a spark gap means being connected in shunt with said charging capacitance means and said outside first power supply, said secondary winding being electrically connectable in series with a second power supply located outside said housing and with said arc lamp.

6. The are lamp housing of claim 5 wherein said charging capacitance means comprises a plurality of capacitors disposed in an annular array around said duct. I

7. The arc lamp housing of claim 6 wherein said capacitors are connected in parallel with each other.

8. The'arclainp housing of claim 5 wherein said transformer core istoroidal surrounding said duct and wherein said charging capacitance means comprises a plurality of capacitors mounted in annular array on an annular circuit board. said circuit board surrounding said duct.

9. The arc lamp housing of claim 8 wherein said spark gap means is mounted on said annular circuit board.

10. The arc lamp housing of claim 9 wherein said circuit board with said capacitors and said spark gap means mounted thereon, said transformer core and said primary and secondary windings are embedded in a dielectric potting compound, said dielectric potting compound being contained between said inner and outer wall surfaces.

II. The arc lamp housing of claim 10 wherein said dielectric potting compound is made of epoxy resin.

12. The are lamp housing of claim 1 in combination with an arc lamp received within said socket means so as to provide a fluid flow path through said duct between said are lamp and said inner wall surface.

13. The combination of claim 12 wherein an array of fins is coupled to said are lamp in heat exchanging rela- 6 tionship with said fluid passing through said duct.

14. The combination of claim 13 wherein said array of fins is annular surrounding said are lamp.

IS. The combination of claim 12 wherein said are lamp has means for focusing light at a point in front of said window, the widest dimension of said window being smaller than the widest cross-sectional dimension of said focusing means.

16. The combination of claim [5 wherein said arc lamp has an array of fins affixed thereto surrounding said widest cross-sectional dimension of said focusing means, said fins being in heat exchanging relationship with said fluid passing through said duct.

17. The combination of claim 12 wherein said are lamp comprises a threaded cylindrical lip portion extending forward of said window, and said arc lamp housing further comprises an adapter member matedly threaded with said lip portion of said are lamp, said adapter member being secured by screws to said cylindrical wall means. 

1. An arc lamp housing which comprises generally cylindrical wall means comprising an inner wall surface and an outer wall surface, said inner wall surface forming a duct, electrical socket means being disposed within said duct for receiving a mating portion of an arc lamp, optical window means located within the duct of said housing, said optical window means being positioned so as to transmit light originating within said housing to the outside of said housing, arc lamp igniting means being disposed between said inner and outer wall surfaces, electrically conductive means extending from said igniting means into said duct for electrically connecting said igniting means to said socket, and means for causing a fluid to pass through said duct to cool said arc lamp during operation of said arc lamp.
 2. The arc lamp housing of claim 1 wherein said means for causing a fluid to pass through said duct is disposed within said duct.
 3. The arc lamp housing of claim 1 wherein said means for causing a fluid to pass through said duct is a motorized fan for causing air to pass through said duct.
 4. The arc lamp housing of claim 3 wherein said fan is disposed within said duct upstream of said socket means with respect to the direction of air flow.
 5. The arc lamp housing of claim 1 wherein said arc lamp igniting means comprises a transformer core, primary and secondary transformer windings in magnetically coupling relationship with said core, said primary winding being electrically connectable in series to a first power supply located outside said housing, electrical resistance means and charging capacitance means being connected in series with said primary winding and a spark gap means being connected in shunt with said charging capacitance means and said outside first power supply, said secondary winding being electrically connectable in series with a second power supply located outside said housing and with said arc lamp.
 6. The arc lamp housing of claim 5 wherein said charging capacitance means comprises a plurality of capacitors disposed in an annular array around said duct.
 7. The arc lamp housing of claim 6 wherein said capacitors are connected in parallel with each other.
 8. The arc lamp housing of claim 5 wherein said transformer core is toroidal surrounding said duct and wherein said charging capacitance means comprises a plurality of capacitors mounted in annular array on an annular circuit board, said circuit board surrounding said duct.
 9. The arc lamp housing of claim 8 wherein said spark gap means is mounted on said annular circuit board.
 10. The arc lamp housing of claim 9 wherein said circuit board with said capacitors and said spark gap means mounted thereon, said transformer core and said primary and secondary windings are embedded in a dielectric potting compound, said dielectric potting compound being contained between said inner and outer wall surfaces.
 11. The arc lamp housing of claim 10 wherein said dielectric potting compound is made of epoxy resin.
 12. The arc lamp housing of claim 1 in combination with an arc lamp received within said socket means so as to provide a fluid flow path through said duct between said arc lamp and said inner wall surface.
 13. The combination of claim 12 wherein an array of fins is coupled to said arc lamp in heat exchanging relationship with said fluid passing through said duct.
 14. The combination of claim 13 wherein said array of fins is annular surrounding said arc lamp.
 15. The combination of claim 12 wherein said arc lamp has means for focusing light at a point in front of said window, tHe widest dimension of said window being smaller than the widest cross-sectional dimension of said focusing means.
 16. The combination of claim 15 wherein said arc lamp has an array of fins affixed thereto surrounding said widest cross-sectional dimension of said focusing means, said fins being in heat exchanging relationship with said fluid passing through said duct.
 17. The combination of claim 12 wherein said arc lamp comprises a threaded cylindrical lip portion extending forward of said window, and said arc lamp housing further comprises an adapter member matedly threaded with said lip portion of said arc lamp, said adapter member being secured by screws to said cylindrical wall means. 